You are wrong, everytime that i have some kind of information about that an altcoin is going to decrease or if just bitcoin is going to do so, i sell all my bitcoins or that altcoin for USDT.
That is the best thing that you can do.
It is the same because you are always going to buy the same amount. 150 USD are the same as 0.01 BTC, and with that amount of money equally in btc or usdt, it is always going to be the same
And once that the altcoin goes down, just buy that one using USDT, by this way you are going to get more bitcoins or whatever you bought.
Simple math, nothing more than that.